Cleaning gas and method for cleaning vacuum treatment apparatus by flowing the cleaning gas

As to a sample produced by forming a WN film of 1 μm thick on a silicon wafer, measurements of etching speed thereto under a condition that a temperature is 500° C., HF gas flow rate is 900 SCCM (90%), O 2 gas flow rate is 100 SCCM (10%). As a result, the lo etching speed was 3045 Å/min which is very high in etching speed. When O 2 gas had not been added, the etching speed was smaller than or equal to a measurement lower limit (≦1 Å/min).

It has not been confirmed of the damages of the apparatus due to the operations for examples 1 to 25.

EXAMPLES 26 TO 36, COMPARATIVE EXAMPLES 6 TO 16

As to Al, Al-alloy 5052 (JIS mark), Al-alloy 6061 (JIS mark), heat-resisting Ni-alloy (trade name: Hastelloy C-22), ferroalloy SUS316L (JIS mark), SUS304 (JIS mark), SUS430L (JIS mark), AlN, Al 2 O 3 , Si 3 N 4 , SiO 2 , corrosion characteristics by gas were observed. More specifically, HF gas (flow rate: 1000 SCCM) and a mixed gas of HF gas (flow rate: 100 SCCM) and N 2 O gas (flow rate: 10 SCCM) were used. The examples were exposed to the gas under a pressure of 500 Torr for 5 hours. After the exposure, the surface of each example was observed by an electron microscope, and the change of weights of each sample before and after the exposure was measured. As a result, it was found that damages to the material were remarkably decreased by adding N 2 O gas. Further, the etching speed of each of the examples 26 to 36 was very high as same as those of the examples 1 to 25. Comparative examples 6 to 16 show the results obtained by the experiments using only HF gas. Also when the gas N 2 O had been changed to one of O 2 , O 3 , NO, CO and CO 2 , the etching speed of this example was high as is similar to those of the examples 1 to 25.

COMPARATIVE EXAMPLE 17

The heat-resisting Ni-alloy (trade name: astelloy C-22) was exposed to the mixed gas of HF gas (flow rate: 1000 SCCM) and O 2 gas (flow rate: 1000 SCCM) at temperature 450° C. and under pressure 760 Torr for 5 hours As a result, the surface of the comparative example 17 was turned to yellow, and corrosive particles were generated.

The heat-resisting Ni-alloy (trade name: Hastelloy C-22) was exposed to the mixed gas of HF gas (flow rate: 1000 SCCM) and O 2 gas (flow rate: 1000 SCCM) at a temperature of 450° C. and under a pressure of 500 Torr for 40 hours. As a result, a transparent passive film was formed on the surface of the example 37. The film was extremely thin and smooth. No corrosion was found on the surface.

COMPARATIVE EXAMPLE 18

The heat-resisting Ni-alloy (trade name: Hastelloy C-22) was exposed to the mixed gas of HF gas (flow rate: 990 SCCM) and O 2 gas (flow rate: 10 SCCM) at a temperature of 450° C. and under a pressure of 0.05 Torr for 40 hours. As a result, the surface of the comparative example 17 was turned to yellow and corroded. By an electron microscope, it was found that projecting substance and particulate material are generated on the surface of the comparative example 18. As a result of XMA observation, it was found that the particles produced on the surface of the comparative example 18 was a metal such as Fe and Ni and F.

COMPARATIVE EXAMPLE 19

An example obtained by forming TiW film of 1 μm thick on a silicon wafer was heated at 500° C., and HF gas (100%, flow rate: 1000 SCCM) was flowed in the reactor for 1 hour. Thereafter, the example was analyzed as to Ti and W by means of an X-ray fluorescence analyzer. As a result, Ti and W were remained on the wafer surface.

An example obtained by forming TiW film of 1 μm thick on a silicon wafer was heated at 500° C., and the mixed gas of HF gas (flow rate: 1000 SCCM) and O 2 gas (flow rate: 1000 SCCM) was flowed in the reactor for 1 hour. Thereafter, the example was analyzed as to Ti and W by means of an X-ray fluorescence analyzer. As a result, Ti and W were not detected on the wafer surface.

EXAMPLES 39 to 52,

COMPARATIVE EXAMPLES 20 to 21

As to a sample produced by forming a Ta film of 1 μm thick on a silicon wafer, measurements of etching speed thereto under conditions shown in Table 5 were executed. The results thereof are also shown in Table 5. As is clearly shown in Table 5, the etching speed was remarkably improved by adding a trace quantity of O 2 gas. Also, when the O 2 gas had been changed to one of O 3 , N 2 O, NO, CO and CO 2 , the etching speed was similarly improved.

EXAMPLES 53 to 60, COMPARATIVE EXAMPLES 22 and 23

As to a sample produced by forming a TaN film of 1 μm thick on a silicon wafer, measurements of etching speed thereto under conditions shown in Table 6 were executed. The results thereof are also shown in Table 6. As is clearly shown in Table 6, the etching speed was remarkably improved by adding a trace quantity of O 2 gas. Also, when the O 2 gas had been changed to one of O 3 , N 2 O, NO, CO and CO 2 , the etching speed was similarly improved.

Next, a cleaning method for practically applying the above-mentioned gas to a vacuum treatment apparatus such as a thin film producing apparatus will be discussed.

FIGS. 1 and 2 show a thin film producing apparatus 2 of a cluster-tool type. The thin film producing apparatus 2 comprises a common conveying chamber 4 which has the form of octagon and is made of aluminum alloy. An articulated conveying arm 6 made of aluminum alloy is provided in the common conveying chamber 4 so as to be rotatable and expandable therein. A supporting portion for supporting a semiconductor wafer 50 to be treated is installed to a tip end of the articulated conveying arm 6 . Four thin-film producing apparatuses 8 A to 8 D are connected to the common conveying chamber 4 through gate valves G 1 to G 4 , respectively. A chamber 20 of each of the thin-film producing apparatuses 8 A to 8 D is made of aluminum alloy and includes a table 10 for setting the wafer 50 thereon, a clamp ring 28 for fixing the wafer 50 on the table 10 , a shower head 24 for flowing gas and an attachment ring therein. The table 10 is made of aluminum alloy. Spare chambers 12 A and 12 B are connected to the common conveying chamber 4 through gate valves G 5 and G 6 , respectively. The spare chambers 12 A and 12 B function as cooling chambers for cooling the treated wafer 50 . Cassette chambers 14 A and 14 B for storing a plurality of the wafers 50 are connected to the common conveying chamber 4 through gate valves G 7 and G 8 . It will be understood that a preheating chamber for preheating the wafer 50 before treatment may be provided as a spare chamber.

The thin-film producing apparatuses 8 A to 8 D, the common conveying chamber 4 , the spare chambers 12 A and 12 B, and the cassette chambers 14 A and 14 B are independently connected to a gas supply line 16 for supplying treatment gas, inert gas such as N 2 gas and the cleaning gas according to the present invention and to a gas evacuating line 18 for evacuating an inner ambient thereof.

In the thin-film producing apparatuses 8 A to 8 D, thin films of Ti, W, Ta, Ru, Ir, the compound thereof and the alloy thereof are produced by the thermal CVD method. Further, the plasma CVD method is executed by the provision of a high-frequency electric source for generating plasma, if necessary.

A representative thermal CVD method executed by using the thin-film producing apparatuses 8 A to 8 D will be discussed with reference to FIG. 2 .

The thin-film producing apparatus 8 A comprises the aluminum-alloy chamber 20 in which the table 10 providing a heater 22 therein is installed. The shower head portion 24 made of aluminum alloy is installed to a ceiling portion oppositely facing with the table 10 . A gas supply port 24 a of the shower head portion 24 is connected to the gas supply line 16 . A plurality of gas outlet ports 26 are provided at a bottom portion of the chamber 20 and are connected to the gas evacuating line 18 . The clamp ring 28 made of AlN (aluminum nitride) is provided around the table 10 so as to fix a wafer 50 on the table 10 . A ring-shaped attachment ring 30 is provided around the clamp ring 28 , as shown in FIG. 2 .

When a thin film of Ti or W is produced on the wafer 50 by using the above-mentioned thin-film producing apparatus 8 A, the thin film is also produced on the inner wall of the chamber 20 , exposed portions of the table 10 , the clamp ring 28 , the attachment ring 30 as an unnecessary film causing particles. The exposed portions of the table 10 are exposed to the cleaning gas. Therefore, it is necessary to execute a cleaning treatment for removing the unnecessary film attached on various portions at regular intervals or irregular intervals.

The examples 1 to 36 are employed in this cleaning method as a cleaning gas. If the examples 26 to 36 shown in Table 4 are employed as a cleaning gas, a mixed gas of HF gas (flow rate: 1000 SCCM) and N 2 O gas (flow rate: 10 SCCM) is used and the pressure is set at about 500 Torr. The cleaning temperature is set at about 500° C. within a range of 450 to 600° C.

In this condition, the etching speed of the cleaning gas with respect to TiN is about 4000 Å/min although this high speed is not shown in Table 4. This speed is generally the same as that in a case that the cleaning executed by means of ClF 3 gas at the temperature ranging from 200 to 300° C. Further, if ClF 3 gas is used at the high temperature 500° C., the table 10 , the shower head 24 , the clamp ring 28 and the attachment ring 30 will be corroded. In contrast, by using the cleaning gas according to the present invention, even at the temperature of 500° C., the corrosion of the various portions in the chamber 20 is prevented. That is, the film producing process is generally executed at the temperature ranging from 600 to 700° C., and the conventional cleaning process was generally executed at a temperature ranging from 200 to 300° C. In contrast, the cleaning process using the cleaning gas according to the present invention can be executed at the temperature ranging from 450 to 600° C. Therefore, the difference between the temperature in the film producing process and the temperature in the cleaning process is largely decreased by employing the cleaning gas according to the present invention. This enables the idling time for varying the temperature to be largely decreased. Consequently, this improves a throughput of the apparatus 2 . Further, it will be understood that cleaning an inner surface of the piping of the gas evacuating line is simultaneously executed with this cleaning of the chamber 20 .

Herein, the cleaning gas may be diluted by mixing inert gas such as Ar, N 2 and He. Further, the cleaning may be executed at predetermined intervals. More specifically, it may be executed at each time when a predetermined number of the wafers were processed, or at each time when an accumulated time period for producing film reached a predetermined time period, or at regular intervals.

Furthermore, an after-treatment of the cleaning process may be executed by evacuating the cleaning gas from the chamber 20 and repeatedly supplying and stopping supplying inert gas such as N 2 gas to the chamber 20 , under a condition that the supply of the cleaning gas is stopped. If the repeated supply and stop of the inert gas are executed several times while evacuating gases from the chamber 20 , the cleaning gas will be rapidly discharged from the chamber 20 .

Additionally, the gas supply port 24 a of the shower head portion 24 may be divided into two ports which are connected to a cleaning gas supply line and a film-producing gas supply line, respectively. If such an arrangement of the plural supply ports 24 a is employed, inert gas such as N 2 gas is flowed in the film-producing gas supply line during the cleaning process. This prevents the cleaning gas from inversely flowing to and remaining in the film-producing gas supply line. Accordingly, the affect of the remaining cleaning gas to the next film producing process is prevented.

Furthermore, although the explanation of the cleaning process is discussed as to the film producing apparatus 8 A, it will be understood that the other film producing apparatuses 8 B to 8 D may execute the normal film forming process during the cleaning process of the film producing apparatus 8 A or may independently execute the cleaning process.

Although the embodiment of the cleaning method has been shown and described such that only the film producing apparatus 8 A executes the cleaning process, it will be understood that several or all of the film producing apparatuses 8 A to 8 D may simultaneously execute the cleaning process together with the common conveying chamber 4 . In this case, the pressures of the respective chambers are equalized at the same pressure by supplying inert gas before the cleaning. Thereafter, the corresponding gate valves are opened, and the cleaning gas is supplied to the respective gas supply line 16 . Furthermore, simultaneously with this supply, the evacuation through the respective gas evacuating lines 18 is executed. This enables the several chambers to be simultaneously cleaned by the cleaning process.

Furthermore, in such a situation, the spare chambers 12 A and 12 B and the cassette chambers 14 A and 14 B may be simultaneously cleaned by this cleaning process.

Although the cleaning gas and method according to the present invention has been shown and described such that the cleaning gas is independently supplied to the film producing apparatus, the common conveying chamber, the spare chamber and the cassette chamber, it will be understood that the present invention is not limited to this embodied method and may be supplied to each of several blocks constituted by several chambers. This enables the number of the gas supply lines to be decreased. Furthermore, if it is arranged such that all of the chambers are simultaneously executed, it is possible to decrease the number of the gas supply lines to one.

Although the embodied cleaning gas and method according to the present invention has been mainly shown and described as to the removal of the thin film of Ti, W, compound thereof and alloy thereof, it will be understood that the invention is not limited to these and may be applicable to the removal of the thin film of Ta, Ru, Ir, the compound thereof and the alloy thereof.

Further, although the embodied cleaning gas and method according to the present invention has been shown and described to employ the CVD method, the invention is not limited to this and may be applied to a vacuum treatment apparatus which generates the above mentioned compound and alloy in a treatment chamber due to a main treatment. Furthermore, although the embodied cleaning method according to the present invention has been shown and described as to the apparatus for treating a semiconductor wafer, the invention is not limited to this and may be applied to an apparatus treating a LCD substrate or glass substrate.

With the cleaning gas and the cleaning method of a vacuum treatment apparatus in accordance with the present invention, it becomes possible to ensure superior advantages. More specifically, by employing the cleaning gas according to the present invention to clean the vacuum treatment apparatus, it becomes possible to remove an unnecessary film deposited in the vacuum treatment apparatus, which produces a thin film of Ti, W, Ta, Ru, Ir, the compound thereof and the alloy thereof, at a relatively high temperature near the film producing temperature and at high etching speed and to prevent the apparatus from being damaged by corrosion. Therefore, it is possible to decrease a difference between the temperatures in film producing process and in cleaning process. This enables the idling time for varying the temperature to be decreased. Consequently, it is possible to remarkably improve an yield factor of products and a throughput of the producing apparatus employing the cleaning gas and the method using the gas according to the present invention.

The entire disclosure of Japanese Patent Application No. 11-302715 filed on Nov. 24, 1999 including specification, claims, drawings and summary are incorporated herein by reference in its entirety.